1. Field of the Invention
The present invention relates to a bicycle frame that comprises pipe members bonded to each other by the use of an adhesive.
2. Description of the Prior Art
Conventional bicycle frames have been manufactured by jointing steel pipes by the process of brazing or resistance welding. As novel materials have recently been developed, for the purpose of making the frames lightweight, materials, such as aluminum alloys or fiber reinforcement plastics, have begun to be used extensively.
When the conventional process is applied to such novel materials, the materials may deteriorate at high temperature. To avoid this problem, the lightweight frames are manufactured by bonding using an adhesive. The manufacture of bicycle frames by means of bonding is advantageous in that large equipment, such as a conventional welder, is not required, and a simplification of the manufacturing process and an improvement in the work environment are expected (which will be a leader in the bicycle manufacturing process in the future).
However, there is a problem when such a bonding is carried out only using adhesive, because there is no industrial standard for reliability or aged deterioration. Therefor, both the bonding and mechanical juncture using screw bolts or rivets must be used so as to give weight for safety. As a result, the manufacturing process becomes complicated. Moreover, the bonding strength at the interface (i.e., the essential characteristic of the adhesive) is reduced, in such a manner that a centralized stress is generated at the portion where rivets or the like are used, or a bonding layer is peeled off by the tip of a screw bolt or a ring when mounted, so that a clearance cannot be kept constant. Also, a gap is created at the interface between the frame and the bonding layer so that water enters into the gap in the market environment and thereby promotes corrosion at the interface.